“Chiral metamaterials” are chiral (i.e., right- or left-handed) artificial materials that include repeating array(s) of small conducting structures (“resonators”) and exhibit a unique macroscopic property due to fine scale repetition of the small conducting structures (e.g., sizes smaller than a wavelength of applied radiation). In particular, chiral metamaterials possessing both negative effective electric permittivity and negative effective magnetic permeability within substantially the same frequency region are believed to behave in very unusual ways when interacting with electromagnetic (EM) radiation, for example: a) bend (refract) light in the ‘wrong’ way (i.e., not a way traditionally known for conventional materials found in nature); b) a flat plate of the material could focus light (act as a lens) instead of dispersing it; c) a light source behind the plate could appear to be in front of it; d) the Doppler effect would be reversed and/or e) surface plasmonic waves could couple to far greater distances from a metamaterial surface than to traditional surfaces such as optical fibers. Such metamaterials that have both negative effective electric permittivity and negative effective magnetic permeability in substantially the same frequency region are generally termed in the art as “double-negative (DNG) metamaterials.”
Chiral metamaterials, especially chiral DNG metamaterials, can have numerous applications in the design of microwave transmission lines, antennas, mode-conversion devices, directional couplers and lenses. Left-handed chiral metamaterials can be of particular use when unusual phase velocity dispersion can be required. For instance, the backward wave couplers, the zero-order resonator, and the zero-order antenna all can utilize the frequency range in which the phase velocity can be very close to zero. Chiral metamaterials can also have a significant role in antireflection coating, microwave and optoelectronic technologies, chemical applications, biomedical imaging. Particularly, there is a need for new optical measurement technologies in biomedical imaging, biotechnology and the drug discovery industry that can benefit greatly from electromagnetic properties of novel chiral metamaterials. For example, drugs are usually sufficiently complex to typically contain one or more chiral centers that result in the existence of stereochemically distinct 3-D structures. For “n” chiral centers in a molecule, there can be 2n different isomers possible and only one isomer of a drug typically has the correct activity. The drug industry has a need to make multiple wavelength optical measurements in order to understand how complex molecular systems, including living cells, can interact with chiral drugs. The unique electromagnetic properties of novel chiral metamaterials might overcome limitations of current optical instrumentation.
Although there have been extensive attention and activity by the optics and engineering community in this new area of materials, understanding of chiral metamaterials and their potential electromagnetic properties are still at a very early stage of development. Also, interest has mainly focused on potential applications in optical communications and signal transmission technology in the microwave region.
Therefore, there is a need to develop methods to understand the electromagnetic wave interaction of chiral metamaterials. There also is a need to develop methods for designing or providing a parameter of new chiral metamaterials, in particular DNG metamaterials, which can be used especially for opto-electromagnetic applications in a visible, ultraviolet or near-infrared region.